Significant advances in recent years in the reduction in physical size and cost of electronic components have resulted from improvements in techniques for the manufacture of microelectronic circuits, e.g. microlithography. Microlithography, generally, comprises applying a film of a radiation-sensitive polymeric material, i.e. a resist medium, to one surface of a substrate, irradiating certain portions of the film with, e.g. ultraviolet light, electron beam, X-ray or the like, and developing the film with a solvent to remove solubilized portions thereof. In the instance of a positive resist, irradiation causes the resist medium to become more soluble in the developer solvent. The resist medium remaining on the surface of the substrate is then employed as a protective mask to facilitate the selective etching or other treatment of the exposed portions of the substrate.
Etching of the substrate may be conventionally carried out by chemical treatment or by plasma discharge. Plasma etching is advantageous because of finer resolution and freedom from pollution and handling problems inherent in the use of chemical etchants. Many resist materials, however, cannot withstand plasma discharge and are eroded along with the substrate resulting in loss of pattern resolution. Therefore, chemical etching is more commonly used in spite of its obvious disadvantages of poorer resolution, posing a pollution threat and being potentially hazardous to operating personnel.
Poly(olefin sulfone) polymers are a major class of such positive resists. Of the large number of poly(olefin sulfone) resist media reported in the literature, however, only one, i.e. poly(1-butene sulfone), is commercially available. Although possessing acceptable sensitivity, this material is disadvantageous in that: it does not adhere well to certain substrates, particularly chromium; it must be irradiated at an electron beam dose of 1 .mu./cm.sup.2 which is at or near the capacity of many installations; and it has poor resistance to plasma etching.
There is a continuing search for polymeric materials with increased sensitivity to irradiation to achieve higher resolution in answer to the demand for ever-finer circuitry. In accordance with this invention, there is provided a positive electron beam recording media which possesses increased sensitivity and development latitude and which has none of the above disadvantages.